1. Field of the Invention
The present invention generally relates to a method of and a device for positioning a biological measurement probe reproducibly relative to a target part of a living body during noninvasive measurement of a biological data such as, for example, the concentration of a particular component in the living body from such target part. More particularly, the present invention relates to the positioning method and the positioning device by which the biological measurement probe can be positioned reproducibly at the target part of the living body to achieve reproducible placement of the biological measuring probe at substantially the same target part throughout a plurality of cycles of biological data measurement to thereby reduce the chances of measurement error.
2. Description of the Prior Art
The noninvasive measurement of biological data (hereinafter referred to as "biodata") on a particular component in the living body has been studied. For example, the noninvasive measurement of the concentration of, for example, glucose in the living body is generally carried out by illuminating a target part of the living body through a measurement probe, detecting transmitted and/or reflected light from the target part and analyzing a spectrum of the transmitted and/or reflected light so detected. As is well known to those skilled in the art, measurement of the glucose concentration in a diabetic patient is generally performed repeatedly on a regular basis. If the position and/or the angle of the measurement probe relative to the target part of the patient change occasionally each time the biodata measurement is carried out, resulting in change of measurement condition, measurement results will no longer be reliable and be irreproducible. Therefore, the measurement results obtained at a certain time of measurement cannot be utilized for significant comparison with the measurement results obtained previously to determine an exact biological condition of the patient that varies from time to time.
The details of how the results of measurement of the glucose concentration become irreproducible as a result of change in position and/or angle of the measurement probe relative to the target part of the patient are discussed in the Japanese Laid-open Patent Publication No. 8-332181 (corresponding to the published International Application No. WO96/41568 published Dec. 27, 1996, or U.S. patent application Ser. No. 08/776,775 assigned to the same assignees of the present invention) and the Japanese Laid-open Patent publication No. 9-49794 (corresponding to the published International Application No. WO97/06423 published Feb. 20, 1997, or U.S. patent application Ser. No. 08/817,085 assigned to the same assignees of the present invention) with the aid of the experimentally obtained biodata.
Accordingly, this type of biodata measurement requires the measurement probe to be firmly positioned in an exact location each time the measurement is carried out. For this purpose, the Japanese Laid-open Patent Publication No. 9-49794 discloses an intelligent measurement system in which the measurement probe is positioned by the use of an image recognition system whereas the Japanese Laid-open Patent Publication No. 8-332181 discloses preparation of a template having an impression complemental in shape to the shape of the target part of the living body by the use of a plasticizeable material so that during the biodata measurement the target part can be snugly received in the impression in the template to position the target part at an exact location, thereby enabling substantially the same target part of the living body to be remeasured.
It has been found that the intelligent measurement system discussed above requires the use of a CCD camera, an image recognition device and an XYZ drive mechanism, making the system as a whole bulky and expensive. On the other hand, although the positioning by the use of the template as discussed above requires a handy device, preparation of the template often encounters difficulty since the target part is apt to deform if it is that of a living body, and therefore, the use of the template would little result in a satisfactory positioning reproducibility.